1. Field of the Invention
The present invention relates to a method for producing ferro-nickel shots, more particularly to a method for easy and rapid mass-production of smooth ferro-nickel shots of a large diameter having a flat-disc or granular shape and containing no water, which method comprises adding manganese to molten ferro-nickel and pouring the molten ferro-nickel containing the added manganese onto a rotating disc to divide and granulate the molten metal, and cooling and solidifying the granules to obtain the shots.
2. Description of the Prior Art
As is well known, ferro-nickel is widely used for production of austenitic stainless steels. The ferro-nickel used for this purpose is usually in the form of ingots similar in shape to cold pig iron ingots and weighing about 100 kg each. In recent years, however, secondary steel making processes, such as the AOD process (Argon-Oxygen-Decarburization process) have come into wide use in the production of stainless steels and steel making operations have been automated in various aspects. The conventional ferro-nickel ingot is not well adopted to these new methods and automated operations because it presents problems in handling and in adjustment of the molten steel composition. As a consequence, a demand has arisen for ferro-nickel in the form of shots or pellets of small diameter.
Conventional methods for production of shots or pellets of metals having high a melting point, such as ferro-nickel, include one in which a jet stream of high pressure fluid, such as air or water, is brought into collision with a molten metal stream to disperse the stream into granules or shots, and another in which a molten metal stream is poured onto a fixed plate to disperse the stream into granules or shots.
The metal slots obtained by the prior art methods very often contain water which becomes unavoidably incorporated therein during the cooling and solidification step. Moreover, the conventional shots lack roundness and are very irregular in shape. In the case of shots produced from a molten metal having high viscosity and small surface tension, such as molten high-carbon ferro-nickel, the shots obtained are exceedingly small in diameter and of flat or needle-like configuration but very irregular in shape. Even if large diameter shots with good roundness could be obtained by the conventional methods there would still be the problem of inner voids.
The main disadvantages of the ferro-nickel shots obtained by the conventional methods can be summarized as follows:
(1) The shots are irregular in shape and have numerous protrusions so that they are susceptible to bridging and are apt to cause clogging while being fed into a steel making furnace with the bunker in which they are stored.
(2) The shots vary greatly in size and, at any rate, are so small that when added to the molten metal, they become suspended in the slag and dispersed into the exhaust gas. As a result, production yields are low.
(3) As the shots very often contain water, there is a danger that they may cause steam explosions when added to the molten metal during the steel making operation.